I'm afraid that as an ex-4th gen owner, I too think the Chevy left the Ford for dead in the styling department - 3rd and 4th gen. I think the Mustang survived because it sold an awful lot of V6 models and was physically more compact and easier to drive so sold more to small families and women - the 4th gen had low seats and it was hard to see any of the extremities if you were short, the doors were long and the hatch was big. The Mustang wasn't as hard-core as the 4th gen, more like a saloon (it still is in many respects), which had gobs more power and handled better although again I think the steering may have been too heavy for many. I think the 4th gen had a pricing issue too from historical agreements to build the F-body in Canada but the fact was you had the cost of an all-alloy Corvette engine too.
The main difference between Ford and GM is that when Ford wanted to kill/replace the Mustang with the Probe, the outcry was enough to change Ford's mind. When they decided to axe the F-Body, despite an outcry, GM did what they always do - exactly what they want. Marketing was never GM's suit and their advertising was very poor.
As for the new Camaro v Mustang, I wouldn't be so confident or arrogant to presume that GM isn't a whole lot more serious this time. It has seen the profit in retro-styling and how a little effort can pay dividends. For the sake of both companies, I hope both the restyled Stang and the production Camaro hit the mark. I'm not too bothered about the Challenger as it's a regeneration of a long-dead 60's model line, bigger, heavier and a different proposition as it's still an old Mercedes under the frock.
Myself, I'm waiting for the Camaro but will be keeping my blown 05 too. If the Camaro is as good as my 4th gen, I may sell the Stang but who can tell, we can only speculate until both players show their cards.